00:02
If a grocer sells oranges for 95 cents and grapefruits for $1 .5 and you purchase a mix of 16 oranges and grapefruits and you pay a total of $15 .90, how many oranges did you buy and how many grapefruits did you buy? so we know there were 16 total pieces of fruit.
00:21
So we're going to say x plus y equals 16.
00:29
We know how much each piece of fruit cost and we know the total amount spent.
00:35
Each orange was 95 cents, so we'll say 0 .95 times x.
00:41
So x is oranges plus $1 .5.
00:47
Y, so y is grapefruit, equals the total amount you spent of $15 .90.
00:57
Over here, x plus y equals 16.
01:00
I'm going to subtract y from both sides, and we get x equals 16 minus y.
01:05
This allows me to use substitution to solve this system of equations.
01:09
I can substitute this whole expression in for x.
01:13
So we get 0 .95 times 16 minus y plus $1 .5 .y equals $15 .90 .0 .95 times 16 is 15 .2 minus 0 .95y plus a dollar 5y equals 1590...